Door Lock issue

[Blue_Mule55]

1995 F 350 one ton dually crew cab E4OD automatic Transmission, 460 EFI gas engine. Issue: Right rear side door lock will not lock. This model is equipped with the keyless entry which did not come with the truck when I bought it ,( meaning I did not get the keyless entry fob with it). In addition it did not have the front door lock key(s) either. SO I bought the door locks ( which came with the keys) from NAPA and they work and secure the truck just fine. The problem I am having is : The right rear side door does not lock at all when I attempt to push down on the door lock. The linkages appear to be in good sturdy order and have no apparent or visible bends to them. What should I be looking at or where do I isolate the problem at? Is it on the actual locking mechanism itself or elsewhere? This model is a power lock model but so far that feature does not work. Suggestions?

 

[blacksnapon]

1995 F 350 one ton dually crew cab E4OD automatic Transmission, 460 EFI gas engine. Issue: Right rear side door lock will not lock. This model is equipped with the keyless entry which did not come with the truck when I bought it ,( meaning I did not get the keyless entry fob with it). In addition it did not have the front door lock key(s) either. SO I bought the door locks ( which came with the keys) from NAPA and they work and secure the truck just fine. The problem I am having is : The right rear side door does not lock at all when I attempt to push down on the door lock. The linkages appear to be in good sturdy order and have no apparent or visible bends to them. What should I be looking at or where do I isolate the problem at? Is it on the actual locking mechanism itself or elsewhere? This model is a power lock model but so far that feature does not work. Suggestions?

Door lock actuator or linkage binding. Time to go inside the door.